Most debilitating neurodegenerative diseases lack effective treatment options. Cell replacement therapy has been proposed as a promising long-term solution. However, procurement of the appropriate cells for therapy has been a significant challenge. Fetal tissue-derived neurons, embryonic stem cell-derived neurons, and induced pluripotent stem cell-derived neurons all suffer from concerns of ethical issues and/or teratoma formation. Transdifferentiation, where an adult cell type can be reprogrammed to another adult cell type of distinct lineage without going through complete de-differentiation to a pluripotent state, represents an attractive approach to generate cells rid of these shortcomings. Neuronal transdifferentiation (NTD) was most recently demonstrated by Wernig et al., where a delivery of Brn2, Ascl2, and Myt1l transcription factors (TFs) to mouse and human fibroblasts converted them into functional neurons with up to 20% efficiency, referred to as induced neuronal (iN) cells. These iNs are postmitotic and do not pass through a proliferative progenitor state, attributes making them an attractive cell source for cell-based therapy of CNS disorders such as epilepsy, stroke, Huntington disease, and Parkinson's disease. However, since these iNs have been generated by lentiviruses, an alternative derivation strategy must be developed for clinical applications. In our preliminary studies we have succeeded in generating mouse and human fibroblasts expressing the pan-neuronal markers Tuj1 and MAP2 by nonviral delivery of the reported TFs. The transdifferentiation efficiency is low, but we believe there is ample room for improvement. The objective of this proposal is to develop effective strategies to generate functional neurons from adult human cells using nonviral methods. We propose to pursue the following specific aims: (1) Optimize efficiency of neuronal transdifferentiation from human adult cells by nonviral vectors; (2) Investigate effects of substrate properties on efficiency of neurona transdifferentiation.